There are many arts which require the measurement of quantities of a powder and the dispensing of such powder. At times a measured powder sample is needed for blending with another powder sample. Pharmaceuticals, powder coatings, confection, powder metallurgy, cosmetics, spices, and flavorings are some examples of areas of technology which have a need for such powder handling methods. There is an especially important need for efficient powder dispensing and distribution in the use of SFF methods. SFF and 3DP use one or more powders dispensed from a reservoir into a container called a build bed to fabricate articles of manufacture. In these methods of fabrication a portion of at least one powder is transferred from the reservoir to the build bed to form a layer of powder. Various techniques are used to form a solid from a portion of the layer of powder. In the case of 3DP a binder is printed onto a layer of powder in a build bed to convert a portion of the layer from a powder into a solid. Successive portions of the same or a different powder are then dispensed and spread over an existing layer in the build bed and subjected to additional printing on selected portions of each successive layer of powder.
It has been disclosed in U.S. Pat. No. 5,204,055 that in a 3DP process a powder being applied in a layer on a build bed can be distributed from a dispensing head passing over a build bed. In U.S. Pat. No. 5,387,380 is disclosed the use of a sieve drum for dispensing powder over a build bed. Both of these disclosed systems and methods of operation suffer from problems. The thickness of a layer of powder deposited on a build bed is known in the art to be an important parameter in how well 3DP or SFF works in manufacturing an article. The thickness of a layer depends on both any method used for compacting the powder, and the amount of powder dispensed onto the build bed. The dispensing head and sieve drum disclosed in these two patents require a complicated multicomponent apparatus adapted for motion over a build bed for their operation. If only one dispensing head or sieve drum is used in a given 3DP or SFF apparatus, then the dispensing head or sieve drum used would require cleaning during a changeover to a second powder if multiple powders were used in the 3DP or SFF fabrication of an article. The complexity of the dispensing head and sieve drum and the risk of cross contamination of powders in a multipowder 3DP or SFF fabrication method are serious disadvantages in the disclosed powder dispensing systems.